Stump grinders with drums with comminuting tools for pulverizing tree stumps in the ground and mixing the wood chips with soil can be used for many purposes other than tree stump eradication. They can for example grind hard material such as asphalt paving as well as breaking up sedimate in a settling pond and then mixing the sedimate with liquid to form a slurry. When the slurry is contaminated sludge, these drums can also mix materials with the slurry that will contain it or neutralize it. Another use for these drive drums with tools on their outer peripheries is the treatment of mine tailings.
My U.S. Pat. Nos. 5,158,126 and 5,355,918, the disclosures of which are incorporated herein by reference, disclose drums driven by a single hydraulic motor. These drums both have relatively short comminuting tools and tool holders that work well for tree stump eradication. When using a drum to treat other materials, different tools and tool holders may be more efficient. A longer drum with additional tools and tool holders can also improve performance for some tasks. It may also be desirable to supply more power to rotate the drum.
The hydraulic motor that drives the drum for a grinder mixer assembly should be protected from the materials being treated and should be isolated from loads that are not directly associated with the transmission of torque to drive the drum. Loads that shorten hydraulic motor life are loads that change the shape of the drum and cause misalignment between the motor housing and the motor spindle. Pressure on one side of the drum can distort the drum if the drum has insufficient strength. The drum can be distorted by the transmission of torque to the tools mounted on its outer periphery. The heat required to attach tool holders to the outer surface of the drum can also cause substantial drum distortion. Tool holders or tool holder attaching brackets are usually welded directly to the outer drum surface. Due to the large loads that may be applied to the tool holders, high heat is applied to the drum to weld the tool holders or tool holder attaching brackets in place. This heat can distort the drum and cause misalignment between a hydraulic motor housing and the motor spindle.
The length of the drum needs to be increased for some uses. With a long drum, potential problems due to torsional deflection of the drum increase. This potential problem increases as the distance along the axis of a drum from tools to the drive torque input to the drum increases. This is due in part to the fact that the tools on the side of the drum that is advancing toward material to be treated absorb most of the torque from the motor. If all the tools and tool holders were loaded equally, the torque would be distributed around the circumference of the drum and distortion of the drum due to the torque load on the drum would be minimized.